What are the most common tumors located in the cerebellopontine angle (CPA)?
Vestibular schwannomas account for 80% - 85% of CPA tumors, meningiomas represent 3% to 13% of tumors in this area; epidermoids make up 2% to 6%; facial or lower cranial nerve schwannomas account for 1% to 2%; arachnoid cysts represent around 1% of the lesions found in this area.
Which cranial nerves is most commonly involved with schwannoma?
Schwannomas most frequently (approximately 90%) arise from vestibulocochlear nerve (CN VIII), with the next most commonly involved nerves being the trigeminal (CN V) and facial (CN VII) nerves, followed by the lower CNs, which include the glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI), and hypoglossal (CN XII) nerves.
What division of the cranial nerve VIII – vestibulocochlear nerve – are most often involved by schwannomas, the superior or the inferior division?
Schwannomas most often involve the inferior division (91.4%), and to a much less extent, the superior division (6%) of the vestibular cranial nerve.
What is the obersteiner-Redlich zone?
The obersteiner-Redlich zone is the transition point between glial and Schwann cells and from the central to the peripheral nervous system.
What is the typical clinical presentation of an acoustic neuroma?
The typical presentation of an acoustic neuroma is unilateral, progressive, nonfluctuating, neurosensory hearing loss with unilateral tinnitus and unsteadiness. Symptoms of facial numbness, vertigo, and gait abnormalities may occur with the continued growth of the tumor.
How is made the diagnosis of vestibular schwannoma?
The diagnosis of a vestibular schwannoma is with a contrast MRI or CT. Contrast is essential because a non-enhanced study can miss small tumors.
Which disease is characterized by bilateral acoustic neuromas?
Neurofibromatosis type 2 - NF II.
What are the options to treat vestibular schwannomas?
Current there are several ways to treat vestibular schwannomas, which include observation – recommended if small or in patients with advanced age with numerous comorbidities, stereotactic radiotherapy, or open craniotomy with surgical resection.
What are the main surgical techniques for the removal of vestibular schwannomas?
The main surgical techniques for the removal of vestibular schwannomas are middle cranial fossa (MF), retrosigmoid (RS) or translabyrinthine craniotomy.
What is the significant disadvantage of translabyrinthine approach?
The distinct disadvantage is the destruction of any functional hearing that may be present before surgery. The translabyrinthine approach eliminates hearing but generally results in the lowest tumor recurrence rate.
There is a large well-defined extra-axial complex mass in the right cerebellopontine angle (CPA) cistern, centered in the internal auditory canal (IAC), which is low signal intensity to grey matter on T1-weighted MR image, and heterogeneous hyperintensity on T2 WI.
Axial contrast-enhanced T1 WI reveals the irregular enhancement of the mass. It shows multiple internal non-enhancing cystic changes. DWI revealed no diffusion restriction of the tumor. There is a disproportionately small amount of edema, given the size of the mass. The lesion measures 4.0 x 3.8 x 3.4 cm.
The tumor extends from the medial aspect of the IAC, which is enlarged and continues through the porus acusticus into the cerebellopontine angle cistern. A sizeable mixed tissue component is present more medially in the CPA, with irregular necrotic or cystic zones interspersed with more cellular tissue.
This mass exerts a mass effect on the right side of the pons, the ipsilateral middle cerebellar peduncle, and the anteromedial part of the right cerebellar hemisphere. The fourth ventricle is compressed and displaced to the left side, and consequently, there is dilatation of the supratentorial ventricular system. There is a widening of the CPA cistern posterior to the tumor, indicating its extra-axial origin.